Edge-lit displays, such as edge-lit signs, under-cabinet lighting, ceiling tile lighting, back light (as a replacement for fluorescent bulbs), generally comprise a light source and a treated light transmitting sheet. The light source illuminates one or more edges of the light transmitting sheet. The sheet is composed of internally light-reflective material such as glass or acrylic. Light that enters the sheet is internally reflected, only escaping where the surface has been treated. The treated area is referred to as an extraction pattern. The extraction pattern may be formed by any suitable means such as etching, sandblasting, engraving, molding in bas-relief, or writing with crayon. Properly implemented, wherever the normally smooth surface has been treated, the surface glows so that it appears to be the light source itself. The glowing areas may take the form of lettering, line drawings, or three-dimensional scenes by layering and applying the appropriate pattern. Various edge light sources may be used, such as neon or fluorescent tubes, light emitting diodes (LEDs), incandescent bulbs or the like.
A problem with conventional edge-lit panels is non-uniform light emission. As light propagates through the light transmitting sheet by total internal reflection, the light energy is attenuated such as by absorption, scattering and diffusion. In general, for a uniform homogeneous light transmitting sheet, these effects become more pronounced with increasing distance from the light source. These effects result in light of non-uniform intensity emitted from the extraction pattern formed on the surface of the sign. Such non-uniformity is manifested as brightly illuminated regions and poorly illuminated regions of the display. Consequently, conventional edge-lit signs are limited in size to approximately 8 to 12 inches in dimension from the light source.
What is needed is edge-lit panels with extractor patterns that produce uniform illumination. Also needed is a reliable and easy-to-use method for adjusting the density of extractor pattern pixels to achieve uniform illumination. The invention is directed to overcoming one or more of the problems and solving one or more of the needs as set forth above.